A crutch user faces the greatest challenge when walking on smooth, wet surfaces. For example, on a rainy or snowy day, rain water or melted snow tracked indoors makes smooth flooring, which would present little or no problem in a dry condition, particularly hazardous. The entrance flooring of many buildings is either vinyl, ceramic, or marble since these materials provide a durable, easily maintained floor surface which is generally acceptable under most conditions. However, when wet, such surfaces are hazardous to crutch users. Therefore, a durable slip-resistant crutch tip which can perform equally well under wet or dry conditions on such surfaces is required.
The ability of a crutch tip to resist slippage is a function of both the shape or configuration of the crutch tip and the material which is used to form the crutch tip, particularly the lower surface or tread piece of the crutch tip which directly engages the floor or other supporting surface. L. Bennett and E. Murphy, "Slipping Cane and Crutch Tips Part I-Static Performance of Current Devices," Bulletin of Prosthetics Research (Fall 1977) appraises the performance of various prior art crutch tips on a variety of surfaces.
With regard to the configuration of the crutch tip, the prior art discloses a friction crutch tip having a lower surface or tread piece which is divided or separated into a plurality of segments, each of which has an edge or portion thereof to provide a separate frictional engagement with the ground or other supporting surface when the tip is flexed. The prior art also discloses a crutch tip having a receiver for a crutch shaft and a skirt. Immediately beneath the receiver, within the skirt, are a rigid plate, an absorption or damping pad, and a ground engageable tread piece. The lower surface of the tread piece includes a plurality of downwardly or outwardly depending projections or fingers for receiving and flexing about small articles while maintaining traction with the ground or other supporting surface.
Typical prior art crutch and cane tips are made of natural rubber. Natural rubber provides superior performance on many of the varied surfaces encountered by a crutch user. However, such natural rubber crutch tips typically provide insufficient traction on smooth wet surfaces. In addition, the performance of such rubber crutch tips may be negatively influenced by such factors as the purity of the latex used in formulating the rubber, the type and quantity of fillers used in the latex, and the hardness of the cured end product.
The prior art discloses inserting one or more disks or strips of non-skid material, such as a metal wire brush, into a rubber crutch tip tread piece in order to improve traction on wet surfaces. Preferably, the non-skid material is inserted at the periphery of the tread piece, rather than in the center and may be affixed to the rubber tread piece by means such as a cementing agent, vulcanization, or a nut and bolt arrangement.
In order to improve the performance of crutch tips on wet smooth surfaces, increase uniformity and reduce cost, various materials have been tested in an attempt to replace the rubber crutch tip. However, natural rubber has an advantage on substantially dry or substantially rough surfaces in that it sloughs off its surface layer when abraded with each step and presents a clean, tacky surface to the supporting surface, in the nature of a rubber pencil eraser. Polyurethane, while an otherwise desirable material, particularly on wet surfaces, does not abrade to the same degree as natural rubber when used on a substantially dry surface, and accumulates a film of dirt, dust and other particles which limits good adhesion to the supporting surface, thereby causing a polyurethane crutch tip to be more slippery than a rubber crutch tip on substantially dry smooth surfaces. The present invention combines the self-cleaning and other advantages of natural rubber on substantially dry or substantially rough surfaces with a more and uniform polyurethane material having a high coefficient of friction on substantially smooth wet or dry surfaces.